This invention pertains to a tool for use as a length element of a pipe string in a well bore to respond to signals from the surface to redirect the flow route of fluid pumped down the pipe string bore.
In many operations involving pipe strings in well bores it is desirable to actuate valves down hole to alter the route of fluid flowing down the pipe string bore. In the past that has been done by various methods including balls and spears dropped down the pipe string bore. In some cases wire lines were run down the pipe string bore to actuate the control or to recover items already dropped down the bore. When valves are used down hole to control moving fluid it is prudent to avoid throttling of flow by valve elements depended upon for positive sealing against leakage. To seal drilling mud, elastomer seal elements are considered essential. If the elastomer is used to throttle fluid flow while closing, the abrasives present often damage the seal surfaces.
In a housing that serves as a length of the pipe string, a selector valve that responds to fluid flow rate manipulations at the surface changes the resistance to the flow of the fluid to cause a piston to move. The moving piston actuates a valve that closes one route and opens another. The preferred embodiment is actuated to close the flow route to the downwardly continuing pipe string and to open a fluid by-pass route through the wall of the pipe string. The piston is spring biased to a starting position to reverse the procedure.
The selector valve has a poppet that is spring biased against the flow of fluid and is moved against the spring by entrainment of the poppet with the flow. It moves axially in response to fluid flow rate changes. The selector valve movement is limited by a cam operating in a serpentine groove that progresses about a periphery. The groove allows the poppet to travel more axially on one excursion than it allows on the next. The poppet can close the valve on one excursion and cannot close it on the next. On the surface, the operator normally stops the mud flow and restarts it to cause the selector valve to make an axial excursion. If the tool is not actuated on that excursion, it will be actuated the next time the flow Is stopped and restarted. Therefore the driller has control of the down hole tool.
The selector valve is carried by the actuator piston. When the selector valve is closed, the piston moves In the direction of flow and operates a slide valve in the process. The slide valve opens transverse holes through the wall of the housing. That permits restricted flow to the well bore. The restriction to flow is enough to maintain enough pressure to keep the actuator piston moved against it""s return spring to prevent valve chatter. The opening action first moves elastomer seals into a sleeve bore then moves the sleeve as a slide valve element to open ports covered by the sleeve. Closing action first moves the sleeve to throttle, and essentially stop the by-pass fluid flow, then moves the elastomer seals into position to serve as a positive closure between sleeve and mating bore.
A salient feature of the slide valve is the ability to positively seal the by-pass route without moving flexible seals over ports. The slide valve is a sleeve that carries the flexible seals over the ports. After the ports are closed by the sleeve, the flexible, positive, seals are moved to seal the narrow opening between the sleeve and it""s mating bore. Friction of the flexible seals within the sleeve causes the sleeve to move with the seals until the sleeve is stopped by positive abutments. A detent arrangement prevents the sleeve from moving during opening of the ports until the seals are within the sleeve bore. No detent is needed with the usual seals to prevent the seals from moving out of the sleeve bore before the sleeve has reached it""s closing travel limit. If seals become available that slide easily within the sleeve bore, a detent arrangement can be provided between sleeve and piston to hold the sleeve in position to protect flexible seals until the sleeve is forced to move relative to the piston by abutments on the housing.